package day34;

import java.util.Scanner;

public class Sloution {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNext()) {
            int num = scanner.nextInt();
            long[] arr = new long[91];
            arr[1] = 1;
            arr[2] = 2;
            for (int i = 3; i < arr.length; i++) {
                arr[i] = arr[i - 1] + arr[i - 2];
            }
            System.out.println(arr[num]);
        }
    }
}
